The invention generally relates to a filtering layout for the purification of the condensate of a power station heated by nuclear means. The present invention comprises a closed vessel with an inlet pipe and an outlet pipe together with a tube sheet located in the tank. The tube sheet divides the inside of the vessel into a filtrate chamber and a turbid chamber and supports a plurality of precoat cartridge filters staggered by rows. The filters project an active surface into the turbid chamber the hollow inside of which communicates with the filtrate chamber. The inlet pipe is seated substantially in the center of the tube sheet and is directed with its opening against a baffle plate located in the turbid chamber.
Nuclear power stations in general, and those with boiling water reactors in particular, require a condensate purification installation with filter layouts of this type in order to attain the necessary reactor water quality. Such installations are commonly known as powder resin precoat filters and, in addition to having significant ion exchange capacity, also have good mechanical filter properties.
A filter layout of this type is known from U.S. Pat. No. 4,609,462. Frequently, such powder resin precoat filters are not satisfactory relative to their service life. A particular disadvantage consists in the case of short service lives of the filters due to the fact that larger quantities of radioactively contaminated resins are obtained, which must be stored as radioactive wastes for long periods of time.
It was found in investigations carried out on completed installations that the causes of the rapidly decreasing service life after a certain operating period are probably the following:
erosion of the resins from the cartridge filters by locally excessive flow velocities;
clogging of the cartridge fabric at the eroded locations by iron oxides so that filtration is no longer possible in these locations;
irreversible clogging of the flow paths in sound areas by the eroded resins and thus further reduction of the active filter surface.
It is further known from comparative experiments that, in the case of reduced filter flow rates and the resulting lower flow velocities, service lives may increase disproportionally, or, at least service life problems occur to a much lesser extent.